The MX Notify Control extension allows you to send customized notifications by emails/PMs based on different triggers - new entry creating/updating, member registration, member validation etc..
MX Mobile Detect is a small plugin that detects if a template was requested by a Mobile Device. You also can detect Screen Resolution!
MX Ajax Detect is a small and simple plugin that detects whether a template was requested by AJAX or not.
Maps is a simple Google Maps fieldtype. Nothing special, nothing complex. Single markers. Drop them in place. Move on. It works with everything : Matrix, Low Variables even Safecracker.
Create QR code (bar code) images.
Marker is an EE 2.x plugin that converts between Markdown and HTML. Both directions are supported, Markdown -> HTML as well as HTML -> Markdown.